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Current and Future Long Baseline Neutrino Experiments
Lee Thompson University of Sheffield
Rutherford Appleton Lab
16th September 2015
Solar neutrino deficit
Atmospheric neutrino deficit
The SNO experiment
• 10,000 PMTs
• 2km underground
• 1000 tons of D20
• 6500 tons of H20
The SNO experiment
SNO results
• ne to nmt oscillations confirmed!
Combined Results
SuperK results (assuming oscillations)
• Re-interpretation of SK results assuming that some fraction of the CR nm have oscillated to nt (that SK is not sensitive to)
3 neutrino mixing • Neutrino oscillations have now been unequivocally observed
using atmospheric, solar, reactor and accelerator neutrinos
• The weak and mass neutrino eigenstates are related via the Pontecorvo-Maki-Nakagawa-Sakata (PMNS) mixing matrix:
• Known knowns: neutrinos have mass and oscillate between flavours; q12, q23, q13, Dm21
2, |Dm322| all measured
• Known unknowns: absolute masses, order of mass states (mass hierarchy), Dirac or Majorana, value of dCP, is q23 maximal / which octant, number of neutrinos
where
sij=sinqij, cij=cosqij,d=CP violating phase
3 flavour mixing • In the above the different matrices relate to
different measurements:
Oscillation Probabilities • In general:
Dm2 = Dm213 ~ Dm2
23 (solar, large) dm2 = Dm2
12 (atmos, small)
Long baseline accelerator neutrino physics
• Uses nm (nm) beams derived from proton-induced pion decay
• nm disappearance is sensitive to q23 and (subleading) to the octant
• ne appearance is sensitive to q13 and (subleading) to the CP phase d
T2K (Tokai to Kamioka)
• 295km long baseline experiment
• Uses 2.5° off-axis nm (nm) beam
• Data-taking started in 2009
• UK contribution to near detector (ND280) includes: – Electronics
– DAQ
– ECAL
• SK far detector
Imperial • Lancaster • Liverpool • Oxford • QMUL • Sheffield • STFC/RAL/DL • Warwick
T2K off-axis near detector
Also there is an on-axis detector (INGRID) used for beam rate and direction measurements
TPCs
T2K beam operation and data taking
• Integrated POT: – Neutrino mode: 7.0x1020
– Anti-neutrino mode: 4.0x1020
Total of 11 x 1020 = 13% of total expected POT
T2K nm disappearance results • Observation of a deficit
of nm events in SK
Published in Phys. Rev. Lett. 112, 181801 (2014)
• Best fit values:
Location of minimum: Dm223
Depth of minimum: sin2q23
World-leading measurement of q23
T2K ne appearance results
Analysis published in Phys. Rev. Lett. 112, 061802 (2014)
• 4.92 ± 0.55 background events expected (no oscillations)
• 28 events observed • 7.3s significance for non-zero q13 • First observation (> 5s) of an
appearance channel signal
T2K joint analysis fit
• Results from a combined likelihood ratio fit to the T2K nm and ne CCQE samples
• Using the PDG 2013 value for q13 there is a preference for dCP ≈ -p/2 and normal mass hierarchy
• Very similar results from an independent analysis based on Markov chain MC
T2K ND280 and systematic errors
T2K anti-neutrino mode running
• Why run with anti-neutrinos?
– Consistency between n and n behaviour, e.g. CPT requires that the disappearance probability in both cases is the same
– Combining data taken in both modes reduces the overall uncertainties on dCP
Ne
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T2K nm disappearance
Results are consistent with T2K neutrino disappearance results (above) and with MINOS anti-neutrino results (below)
MINOS / MINOS+
• MINOS – 735km baseline, FNAL to Soudan – 1kt near detector 1km from source – 5.4kt far detector – Both ND and FD are steel-plastic
scintillator calorimeters – UK contributions
• DAQ, electronics, PMT testing, light injection
• MINOS+ – Uses updated NUMI beamline – Higher energy (cross-checks with
different beam and cross-section systematics
– More statistics (4000 nm CC events/year in far detector)
Cambridge • Oxford • STFC/RAL • Sussex • UCL
MINOS/MINOS+ combined fit •MINOS+ has accumulated 6.4x1020 POT from FNAL NUMI beam •Largely focussing on exotic searches (sterile neutrinos, etc.) •Combined MINOS/MINOS+ fit is consistent with previously reported MINOS results
NOnA experiment and status Sussex
Far Detector,
Ash River • Precision appearance/disappearance nm (nm) measurements • 810km long baseline experiment • Off-axis narrow band FNAL NUMI neutrino beam • 209t near detector and muon catcher • Far detector 14kt totally active liquid scintillator
ND and FD as similar as possible to minimize systematics when using the large ND flux to predict the unoscillated FD spectrum
UK contribution: data driven trigger, stopping muon calibration, nm analysis
NOnA far detector data
NOnA candidate nm event
NOnA nm disappearance results
Dm322 2.370.15
0.16
Dm322 2.400.17
0.14
sin2q23 0.51 0.10
(normal hierarchy)
(inverted hierarchy)
201 events expected, 33 observed 8% of nominal exposure
NOnA candidate ne event
NOnA ne appearance results
• Results from 2 independent analyses using different particle ID algorithms • Commented at NuFACT: both analyses “prefer” NH and dCP=3p/2
NOnA and T2K complementarity
• Combining NOnA and T2K data helps break degeneracies and improves coverage in the overlap regions
• Mainly due to NOnA ‘s increased sensitivity to the mass hierarchy via matter effects
Mixing angles and mass differences
Current understanding
• Global fit data as of June 2014 • Uses LBL, SBL, reactor, solar, atm data • Uses technique in Capozzi et al. PRD
89 (2014) 093018)
Normal Inverted
Mass hierarchy
HyperK beam and detector • 295km baseline • Large volume water Cerenkov • 990kT total volume • 560kT fiducial volume (25x SK) • 99,000 PMTs (20% coverage) • 10 optically isolated compartments
• J-PARC nm (nm) beam upgraded to ≥ 0.75MW
• 2.5° off-axis, narrow band 600MeV beam
HyperK status
• In 2013 Japan granted a 5 year £2.3M R&D grant which includes provision for a prototype detector (+$1.2M)
• In early 2014 the Science Council of Japan selected HyperK as one of its top 27 scientific projects in its 2014 Master Plan
• Discussions with Japanese funding agency, MEXT, in progress for long-term funding
• Current Collaboration>240 people • UK represents the second largest group of scientists after Japan
HyperK timeline
HyperK ne(ne) appearance events
• Neutrino mode: dominant background is intrinsic ne contamination from the beam
• Anti-neutrino mode: also large wrong-sign background
Appearance ne events Appearance ne events
7.5 x 107 MW sec, sin22q13 = 0.1, dCP=0, normal MH, n:n = 1:3
HyperK nm(nm) disappearance events
• Anti-neutrino mode: significant wrong-sign nm contribution
Disappearance nm events Disappearance nm events
7.5 x 107 MW sec, sin22q13 = 0.1, dCP=0, normal MH, n:n = 1:3
HyperK sensitivity to CP
Assuming 7.5x107 MW sec: • CP violation can be observed
at – 3σ for 76% values of δCP – 5σ for 58% values of δCP
• δ can be measured with – 8° precision for δ = 0 – 19° precision for δ = π/2
HyperK broad scientific programme
HyperK UK involvement Edinburgh • Imperial • Lancaster • Liverpool • Oxford
QMUL • RHUL • Sheffield • STFC/RAL • Warwick
Work Package Deliverables
WP1: Physics, Software and Computing
interface GENIE neutrino interaction generator with Hyper-K; software release and data distribution
WP2: Detector R&D design of TITUS, a water Cerenkov near detector TITUS; inform the decision on Gd-doping; selection of the photo-sensor technology for near and far detectors; conceptual design of HPTPC near detector.
WP3: DAQ Design of a functional, flexible system that will meet the physics requirements of the experiment. A small-scale DAQ test system will be demonstrated using a prototype detector located in Japan.
WP4: Calibration Delivery of a fibre-coupled pulsed light source; Fixed point diffuser; Pseudo-muon light source.
WP5: Beam Identify critical materials issues for reliable beam window and target operation at multi-MW beam powers; specify materials test programs; select preferred target technology and plan the necessary research programme
HyperK UK WP2 Detector R&D • TITUS
– 2kt Water Cerenkov surrounded by MRD situated at 2km from beam source (sees almost identical spectrum to HK)
– Possibly Gd doped to improve n/n and ne/nm
separation
22m
• PMT/LAPPD studies
– Gd doping
HyperK UK WP4 Calibration • Pseudo light-source:
– Short duration light pulses from LEDs
– Light coupled into optical fibres
– Fibre ends inject light directly into the detector
– Illuminate multiple PMTs on other side of a tank
– Continuous low pulse rate operation during data taking
– Electronics (which may require intervention) is easily accessible
– LED pulser circuit designs under consideration include modified Kapustinsky, 4 MOSFETs in H bridge
• Pseudo-muon light source: – Objective is to inject a Cherenkov-
like cone of light into the detector
– Can be achieved using a short, narrow transparent (acrylic) tube along with a light source which produces almost parallel light
– Different muon momenta can be simulated by using different lengths
– Electronics (which may require intervention) is easily accessible
– LED pulser circuit designs under consideration include modified Kapustinsky, 4 MOSFETs in H bridge
Water Č: Gd loading Turn a standard Water
Cherenkov detector into a anti-neutrino detector by loading with ~0.2% water soluble Gd
Use delayed (~30ms) coincidence of g and e+
90%
10%
The problem is that you need to completely remove the Gadolinium Sulphate when necessary need a selective GD filtration system
New system based on nano-filtration. Molecular band-pass filter analogous to electrical equivalent
EGADS: 200ton Gd demonstrator close to Super-K
Initial results show 66% Č light left at 20m with Gd c.f. 71% to 79% without
Recent decision to run SK with Gd
DUNE status
• DOE CD-1 preliminary baseline approval in December 2012 – DOE commitment of $867M to LBNE – Plus PIP-II for 1.2MW beam – total of $1.5B
• Funding bids in process/successful in UK, India, Brazil, Italy,… • UK is largest non-US group represented ~10% of collaboration
Mark Thomson seminar next week
• Far detector – Up to 40kt fiducial volume – Staged approach 4 x 10kt in
separate caverns – Allows different designs to be
considered (single vs double phase)
• Wide band FNAL neutrino beam
• 1.2MW upgradeable to 2.3MW
• 0.5 – 5.0 GeV sign-selected n
• Near detector design in progress
DUNE beam and far detector
Beamline visualisation
Liquid Argon TPCs Why Liquid Argon?
High density, cheap
Dense good target
Excellent dielectric properties support large voltages
Free electrons from ionizing track can be drifted in long distances inLAr
Electron cloud diffusion is small
High scintillation light yield (at 128nm) can be used for triggering
Why a Liquid Argon TPC?
Combines the principles of a gaseous TPC with a LAr calorimeter
Fine grained tracking
High granularity dE/dX
True 3D imaging with mm-scale spatial resolution
Excellent PID
Constantly sensitive
ArgoNeut event Dri
ft d
irec
tio
n
Liquid Argon TPCs: Challenges Technical challenges:
to achieve long drift distances ultra-high purities (better than 100 ppt O2 equivalent) are required
Drift field requires HV on the cathode
Operation of large wire chambers at cryogenic temps
No charge amplification in liquid fC charges requiring sensitive preamps
Large number of R/O channels
Large cryogenic systems
A Rubbia, Neutrino 2012
Calorimetric Performance:
ICARUS data (2004) with Michel electrons from stopping muon decay
MC expectations (higher E):
Liquid Argon TPCs: performance Tracking Performance:
Data taken in test beams with prototypes (e.g. 250l T32 experiment at J-PARC)
Hit charge distribution fitted well with Birks Law
48
Q AQ0
1 (k ) (dE dx) (1 p)
sEE
11%
E 4%
sEMMC
E3%
E1%
sHAD
MC
E15%
E10%
LAr prototyping activities
• Plans to test full scale LBNE drift cells in 8m x 8m x 8m cryostat at CERN (WA105)
• Programmes provide short term physics and analysis opportunities
• DUNE 35 ton prototype due to take data at FNAL in late 2015
• LAr1-ND, 82t TPC for MicroBoone (2017) • Other activities ArgoNeut, LARIAT etc.
DUNE Timeline
Far detector appearance probabilities
• Appearance probabilities at 1300km as a function of neutrino energy and dCP value
• Value of dCP affects both frequency and amplitude of oscillation
• Black line: probability if q13=0
n n
NH
DUNE far detector event rates
DUNE MH sensitivity
• Significance for mass hierarchy determination as a function of dCP value for 300 kt.MW.years (approx 7 years of running)
• Mass hierarchy determined with a significance of 5 or higher for 100% of dCP values (optimised beam design)
DUNE dCP sensitivity
• Significance for CP violation determination as a function of dCP value for 300 kt.MW.years (approx 7 years of running)
DUNE UK involvement Cambridge • Lancaster • Liverpool • Manchester • Oxford
Sheffield • STFC/RAL • Sussex • UCL • Warwick
Work Package Deliverables
WP1: Physics Simulation and Experiment Design
Oscillation physics simulation; GENIE-LArSoft interface; Near detector design studies; Target and beam design; Beam systematics study;
WP2: Neutrino Event Reconstruction
Pattern recognition software (PANDORA) and interface to LArSoft; neutrino event reconstruction;
WP3: DAQ DAQ for 35t prototype; data compression and event triggering; DAQ architecture design and prototyping.
WP4: 35t Prototype HV monitoring cameras; operation and commissioning; simulation and data analysis; rejection of cosmic-induced backgrounds.
WP5: TPC Design and Construction
LAr1-ND APA and CPA frame design, wiring, cold-testing, construction and installation; LBNE APA and CPA design.
DUNE UK WP2 Event Reconstruction • Neutrino events in a LAr
TPC give high resolution, bubble-chamber like images
• The challenge is to go from this to reconstructed physics quantities
• PANDORA-based event reconstruction and LAr pattern recognition tools being developed
DUNE UK WP5 APA design • UK-built 35t APA undergoing
LN2 cool down tests
• APA wiring frame concept design
• LAr1-ND: UK proposes to build
• One of the two APAs
• The CPA and HV feedthrough
Systematics • With the promise of high statistics in the next generation long baseline experiments systematics will play a major role
• E.g. consideration of – Neutrino cross-
sections – Beam flux
uncertainties
Non-accelerator based oscillations - SK Next 3 Slides from Alex Sousa’s summary talk at NuFACT’15
Non-accelerator – IceCube + DeepCore
Non-accelerator future – PINGU/ORCA
Conclusions
• Neutrino oscillations are now well-established and experiments are in a phase of accurately measuring the parameters of the PNMS mixing matrix
• In recent years a non-zero q13 mixing angle has been observed – thus opening the door to a search for CP violation
• Current and proposed projects have excellent prospects for measuring dCP and determining the neutrino mass hierarchy
• There is a well-defined global programme of long baseline experiments reaching well into the late 2020s
T2K ne appearance
CHIPS concept
• CHIPS is a water Cherenkov detector which will be sunk in a flooded mine pit in the path of the NuMI beam
• Water will provide mechanical support • Its main development goal is to chart a
new path towards cost effective Megaton neutrino detectors, hoping to get to $200k/kt (presently $1M/kt)
• Complements NOnA (being more on-axis) and DUNE (more off-axis) when redeployed in the LBNF beamline
• Consists of a series of prototypes which will deliver physics results and demonstrate real costs for (O)100kt
• Proposed site is the Wentworth pit in Minnesota
• UK-led work packages include – Simulation and reconstruction – DAQ – In-situ calibration
Manchester • UCL
CHIPS Physics Goals • Short term:
– Contribute to the measurement of dCP using neutrinos from the NuMI beam by measuring the sub-dominant ne appearance and rejecting the NC background
– Building and instrument a 10kt prototype
• Medium term: • ~25kt (TBD) vessel to follow) • Yearly increase of instrumented
mass depending on funding – Deployment seasonal – Large up-front funding not
necessary – Staging of detector(s) natural
• Long term: • Re-deploy CHIPS in LBNF beam off
axis • 2nd oscillation maximum located
around 0.8 GeV – Large quasi-elastic x-section – Suitable for water Cerenkov
detector • High efficiency for QE events
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